1. Field of Invention
The present invention relates to a display apparatus and a signal processing method thereof. More particularly, the present invention relates to a display apparatus capable of effectively processing a Vertical Blanking Interval (VBI) data signal contained in an input analog image signal, and a signal processing method thereof.
2. Description of the Related Art
In broadcasting standards, such as National Television System(s) Committee (NTSC), Phase Alternation Line (PAL) and Séquentiel couleur avec mémoire (SECAM), a vertical blanking interval (VBI) data signal is overlapped in the VBI of an image signal. The location of the vertical blanking interval where a VBI data signal is contained in an image signal is defined in accordance with each of the broadcasting standards.
The VBI data signal contains various additional information, such as closed caption information, teletext information, copy generation management system (CGMS) information, and sound multiplex index information.
For example, in a one-frame image signal of the NTSC standard having 525 horizontal lines, an odd field comprises a vertical blanking interval (VBI) comprising 21 horizontal lines and an image display interval ranging from the 22nd to 262nd horizontal lines. In each of the horizontal lines within the image display interval is contained an effective image signal. On the other hand, the vertical blanking interval is divided into three equalization pulse intervals (EQIs) comprising 9 horizontal lines and an additional information interval (AII) comprising 11 horizontal lines.
As for a VBI data signal contained in a conventional analog image signal, a traditional method is used in which data is captured by means of slicing a corresponding signal level in accordance with an operation of an analog circuit in a microcomputer or an analog decoder corresponding thereto. The data is then decoded and then displayed on-screen.
However, if the signal level of an input analog image signal is weak or there is generated noise, a VBI data signal contained therein is damaged and causes an error so that the erroneously recovered data is displayed on-screen.